Switching voltage regulators are widely used in modern electronic systems for a variety of applications such as computing (server and mobile) and POLs (Point-of-Load Systems) for telecommunications because of their high efficiency and small amount of area/volume consumed by such converters. Widely accepted switching voltage regulator topologies include buck, boost, buck-boost, forward, flyback, half-bridge, full-bridge, and SEPIC topologies. Multi-phase buck converters are particularly well suited for providing high current at low voltages needed by high-performance integrated circuits such as microprocessors, graphics processors, and network processors. Buck converters are implemented with active components such as a pulse width modulation (PWM) controller IC (integrated circuit), driver circuitry, one or more phases including power MOSFETs (metal-oxide-semiconductor field-effect transistors), and passive components such as inductors, transformers or coupled inductors, capacitors, and resistors. Multiple phases (power stages) can be connected in parallel to the load through respective inductors to meet high output current requirements.
Steep load transients (e.g. a step-up transition from 0 A or near 0 A to 200 A or more in less than 1 μs) typically require extensive and costly capacitor decoupling solutions to prevent the output voltage from falling below or rising above a specified limit. Regulator topologies that utilize inductive coupling to the load have an inherent limitation on the bandwidth with which the regulator can respond, due to the limited current ramp rate (slew rate) through the output inductors used to couple the regulator to the load. Conventional regulator controllers typically have transient support features for enabling all phases of a multiphase regulator to simultaneously source or sink current. Also, bypass switches have been used to discharge the output capacitor if needed. Regulator phases for supporting only AC content have been used as a bypass to the regulator. However, general improvement of regulator bandwidth requires smaller inductor values and higher switching frequency at the expense of efficiency. As such, a solution for handling steep load transient events which does not require a larger output capacitor, smaller output inductors, large bypass switches and/or an increased number of phases is desirable.